A: Both are similar in content. Dinesh has better color diagrams and paper quality (in physical form). S.L. Arora has more previous years' questions. For "extra quality PDF," Dinesh scans better due to its clean layout.

Scan every downloaded file. Use VirusTotal.com (upload the file or paste the URL) before opening.

A: Use "PDF Wipe" or "Adobe Acrobat Pro" (trial). However, watermarks are often placed by piracy sites to track you. Legal e-books have no watermarks.